Ductilizing process



Patented Dec. 28, 1937 PATENT OFFICE DUGTILIZIN G PROCESS John R. Gier, Jr., Penn Township, Allegheny County, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania UNITED STATES No Drawing. Application September 13, 1935, Serial No. 40,417

2 Claims. (01. 14s 11.s)

My invention relates to processes for improving the ductility of metallic compositions, and it has particular relation to a ductility treatment for compositions containing principally iron and 5 cobalt.

Many alloy compositions of this class have magnetic properties of special value. In general, however, such materials are quitebrittle and hence difiicult to fabricate into the desired final forms unless hot-forging, hot-rolling or casting operations are resorted to.

Where small sections, such as thin sheet material or small diameter wire and other comparatively delicate magnetic parts for the making of which the iron-cobalt alloys under discussion are of special advantage, are to be produced, these hot forming operations present a number of rather serious disadvantages. Thin sheets for example, cannot be punched without cracking nor can the material be conveniently formed into small wires or the like.

Generally stated, the object of my invention is to overcome the disadvantages above named.

A more specific object is to provide a ductilizing process which permits thin sections of iron-cobalt alloy to be fabricated by relatively inexpensive cold working processes.

, In practicing my invention, I subject conventionally prepared alloy material to .a substantial 3O mechanical deformation under special temperature conditions and then follow this by a heat treatment involving a rapid quenching from a comparatively high temperature. The combined effect converts the originally brittle alloy into a 35 material sufficiently malleable and ductile to be cold formed into practically anyfinal shape desired.

For application to an alloy comprising substantially 49% iron, 49% cobalt and 2% of one 40 or more additional elements of which vanadium is representative, the preferred conditions under which my improved ductilizing process may be carried out will now be described.

Alloy material which has been reduced in conventional manner by the usual series of rolling operations into sheet form is first subjected, at a temperature preferably between 550 and 650 C. to a deformation equivalent to approximately 20% reduction in sheet thickness. This deformation may conveniently be produced by one or more passages through a rolling mill.

In this state the material is then rapidly heated in a furnace to between 900 C. and 975 C. Preferably a fused salt bath is used to obtain a higher heating rate and greater uniformity thereof. As

soon as up to temperature the material is immediately removed and cooled at a rapid rate characteristic of quenching in brine or water. This step of the process may conveniently be carried out by immersing the heated material directly into an appropriate quantity of water or other room-temperature liquid.

When thus treated, strip material of thicknesses up to 0.125 inch or more, normally very brittle when cold, exhibits malleability and ductility characteristics in sufiicient degree to permit cold rolling into such lesser thickness as may be desired or other form of fabrication into the final magnetic or other device parts.

Such magnetic properties as may have been diminished during this treatment may be restored or developed by known forms of heat treatment, one convenient method of which is to heat the material at around 900 to 1100 C. for approximately one hour in the annealing pot of an electric furnace, for example, and then let the material there contained cool down to room temperature before removing from the furnace. The fact that the material may thereby again become brittle and non-workable is of little consequence, since it already is in the final form in which it will be employed.

In certain cases where breakage is not important the described quenching may itself be sufficient to effect proper ductility improvement. In the majority of situations, however, the mechanical deformation described as preceding the quenching is found essential to render the alloy more amenable to the heat treatment. As without it brittle areas frequently remain, its use is recommended. This is particularly important in the rolling of long strips where breakage would greatly complicate the treating operations.

My improved ductilizing process is not restricted in application to alloys having the particular composition above named only, but it may also be applied with advantage to a wide variety of other iron-cobalt base compositions. Magnet steels of the type made up, for example, of 36% cobalt, 57% iron, 4% chromium, 2% tungsten and 1% carbon may be comparably benefited either by making the alloy without the carbon or by decarburizing. After ductilizing and working into the desired final form the carbon may be introduced by any conventional carburizing process. This in turn may be followed by heat treatment proper for imparting the desired magnetic properties.

Ductility improvement appears to result chiefly from a peculiar change in the lattice structure the alloy to between 900 C. and 975 C. and quenching the alloy to cool it at a rapid rate.

2. A process for improving the ductility of an iron cobalt alloy that has been reduced by a conventional rolling operation which comprises further working the alloy between 550 C. and 650 C. to deform it by an amount substantially equal to a 20% reduction in section, raising the temperature of the alloy to between 900 C. and.

975 C. and quenching the alloy to cool it at a 10 rapid rate.

JOHN R. GIER, JR. 

